A Level Biology Practice Exam

What is transpiration in plants?

1. Uptake of water from the soil

2. Loss of water vapor from aerial parts

3. Translocation of nutrients

4. Photosynthesis process

The correct answer is: Loss of water vapor from aerial parts

Transpiration is the process through which plants lose water vapor from their aerial parts, primarily through small openings on the underside of leaves known as stomata. This process is vital for several reasons. First, it helps in the uptake of nutrients and minerals from the soil by creating a negative pressure in the plant's xylem, facilitating the movement of water and dissolved substances from roots to leaves. Additionally, transpiration plays a crucial role in regulating temperature within the plant, as the evaporation of water helps cool leaf surfaces, preventing overheating. It also contributes to water cycling in the environment. The other choices describe different processes: the uptake of water from the soil pertains to root function, translocation of nutrients involves the movement of sugars and other compounds through the phloem, and photosynthesis refers to the process of converting sunlight into chemical energy. Each of these processes plays an important role in a plant’s overall physiology but they do not define transpiration.